\chapter{Background}\label{cha:backgrounds}
The work of the thesis is based on the Wi-Fi platform and using the Host
Identity Protocol as building block. This chapter describes briefly the 
related background information.
It gives firstly an overall introduction to the
Wi-Fi technology. The Host Identity Protocol
itself, which we used and modified will then be
introduced. Since HIP utilizes IPsec  to protect the transmission
of the payload, we give a short presentation about IPsec
and how HIP and IPsec work together. 
We also give a brief introduction to 
the Network Address Translation (NAT), which we must handle in the Wi-Fi
sharing environment. 

\input{bg_wifi}
\input{bg_hip}
\input{bg_ipsec}
\input{bg_crypto}
\input{bg_nat}


